A repeating fast radio burst source in a globular cluster.

Fast radio bursts (FRBs) are flashes of unknown physical origin1. The majority of FRBs have been seen only once, although some are known to generate multiple flashes2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission4,5. Recently, the discovery6 of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths6. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system7. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.

[Mood disorders in HIV patients: a challenge for liaison psychiatry consultation]. / Troubles de l'humeur et VIH: épidémiologie, clinique et prise en charge thérapeutique.

Mood disorders represent the most prevalent psychiatric condition in patients infected by HIV virus. Screening and treatment of depression as well as the evaluation of the risk suicide is of the utmost importance. When psychopharmacological treatment is required, interaction with antiretroviral treatment must be carefully considered. More generally a close collaboration between the physician and the psychiatrist is recommended.

Target-specific expression of presynaptic mossy fiber plasticity.

Mossy fiber synaptic transmission at hippocampal CA3 pyramidal cells and interneurons was compared in rat brain slices to determine whether mossy terminals are functionally equivalent. Tetanic stimulation of mossy fibers induced long-term potentiation in pyramidal neurons but was either without effect or it induced depression at synapses onto interneurons. Unlike transmission onto pyramidal neurons, transmission onto interneurons was not potentiated after adenosine 3',5'-monophosphate (cAMP) activation. Furthermore, metabotropic glutamate receptor depression of transmission onto interneurons did not involve cAMP-dependent pathways. Thus, synaptic terminals arising from a common afferent pathway do not function as a single compartment but are specialized, depending on their postsynaptic target.

Passive propagation of LTD to stratum oriens-alveus inhibitory neurons modulates the temporoammonic input to the hippocampal CA1 region.

Excitatory synaptic activity in horizontal stratum oriens-alveus interneurons (OAIs) is driven by the recurrent collaterals of CA1 pyramidal cells and is strongly influenced by protocols that elicit synaptic plasticity in these principal neurons. Induction of LTD in the Schaffer collateral-CA1 pyramidal neuron synapse causes a passive down-regulation of stratum radiatum-evoked excitatory synaptic responses onto OAIs. In addition, we show that the strength of the temporoammonic input to the CA1 pyramidal neuron distal dendrites is regulated by OAI activity. The passive propagation of LTD to OAIs consequently disinhibits the direct entorhinal cortex-CA1 input, resulting in an enhanced excitation of CA1 pyramidal neurons by a mechanism not requiring activation of the trisynaptic pathway.

Anti-N-Methyl-D-Aspartate Receptor Encephalitis: A New Challenging Entity for Consultation-Liaison Psychiatrist.

BACKGROUND: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is a relatively newly identified autoimmune neuropsychiatric disorder that predominantly affects children and young adults. Although psychiatric symptoms are highly prevalent and frequently severe, it has mainly been reported in neurological, but not psychiatric, literature. Understanding this form of encephalitis, its quick diagnosis and which treatment to provide are of utmost importance for consultation-liaison (C-L) psychiatrists. The aim of this paper was to describe a case of anti-NMDAR encephalitis with severe psychiatric manifestations, who showed impressive recovery but required intensive involvement of the C-L psychiatry team. We emphasise the behavioural aspects, psychiatric symptoms and challenges faced by the CL consultant across the different phases of the treatment. METHODS: We report the different treatment phases for a young woman with anti-NMDAR encephalitis who developed severe neuropsychiatric symptoms, with a focus on the role and challenges faced by the C-L psychiatrist. The literature is reviewed for each of these challenges. RESULTS: This case illustrated that even extremely severely affected patients may show impressive recovery, but require long lasting psychiatric care. C-L psychiatrists are faced with numerous challenges where only little literature is available. CONCLUSION: C-L psychiatrists play a pivotal role throughout the multidisciplinary care of patients with anti-NMDAR encephalitis and should be informed about this entity.

Efficacy of brief interdisciplinary psychotherapeutic intervention for motor conversion disorder and nonepileptic attacks.

OBJECTIVE: The objective was to compare a brief interdisciplinary psychotherapeutic intervention to standard care as treatments for patients recently diagnosed with severe motor conversion disorder or nonepileptic attacks. METHODS: This randomized controlled trial of 23 consecutive patients compared (a) an interdisciplinary psychotherapeutic intervention group receiving four to six sessions by a consultation liaison psychiatrist, the first and last sessions adding a neurological consultation and a joint psychiatric and neurological consultation, and (b) a standard care group. After intervention, patients were assessed at 2, 6 and 12 months with the Somatoform Dissociation Questionnaire (SDQ-20), Clinical Global Impression scale, Rankin scale, use of medical care, global mental health [Montgomery and Asberg Depression Rating Scale, Beck Depression Inventory, mental health component of Short Form (SF)-36] and quality of life (SF-36). We calculated linear mixed models. RESULTS: Our intervention brought a statistically significant improvement of physical symptoms [as measured by the SDQ-20 (P<.02) and the Clinical Global Impression scale (P=.02)] and psychological symptoms [better scores on the mental health component of the SF-36 (P<.05) and on the Beck Depression Inventory (P<.05)] and a reduction in new hospital stays after intervention (P<.05). CONCLUSION: A brief psychotherapeutic intervention taking advantage of a close collaboration with neurology consultants in the setting of consultation liaison psychiatry appears effective.

Calcium channels in undifferentiated PC12 rat pheochromocytoma cells.

Undifferentiated rat pheochromocytoma PC12 cells were voltage clamped using the whole cell technique. After blockade of outward currents, calcium currents were elicited from -40 and -100 mV. A subpopulation of cells displayed only one current component activated at -10 mV and slowly decaying. In other cells this current coexisted with a component activated around -40 mV and decaying with a faster time constant. We conclude that undifferentiated PC12 cells can express two types of calcium channels, L (long-lasting) and N (neuronal)-type channels.

Complex effects of CNQX on CA1 interneurons of the developing rat hippocampus.

We have investigated the effect of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), on spontaneous GABA(A) receptor-mediated transmission in the hippocampal CA1 subfield. On average, simultaneous recordings from CA1 str. radiatum interneurons and pyramidal cells showed that CNQX application doubled the frequency of bicuculline sensitive spontaneous inhibitory postsynaptic currents (sIPSCs) without apparently changing their amplitude. However, despite the increase in sIPSC frequency, current-clamp recording showed that CNQX application was sufficient in most cases to depolarize interneurons to firing threshold. In contrast, CNQX application could not induce firing in pyramidal cells. In the presence of tetrado-toxin (TTX), CNQX increased interneuron membrane conductance, and depolarized interneurons from resting potentials. The axons of the studied interneurons ramify widely in the CA1 region and suggest that the cells of our sample are mostly involved with control of dendritic excitability. Our results indicate that CNQX-induced increase of sIPSC frequency is not limited to excitatory cells, but also impacts GABAergic interneurons. However, despite the increase of sIPSC frequency, CNQX-induced depolarization is sufficient to selectively generate firing in interneurons and thus modify the network properties mediated by GABA(A) receptors in the hippocampus.

Cholecystokinin-immunopositive basket and Schaffer collateral-associated interneurones target different domains of pyramidal cells in the CA1 area of the rat hippocampus.

Two types of GABAergic interneurone are known to express cholecystokinin-related peptides in the isocortex: basket cells, which preferentially innervate the somata and proximal dendrites of pyramidal cells; and double bouquet cells, which innervate distal dendrites and dendritic spines. In the hippocampus, cholecystokinin immunoreactivity has only been reported in basket cells. However, at least eight distinct GABAergic interneurone types terminate in the dendritic domain of CA1 pyramidal cells, some of them with as yet undetermined neurochemical characteristics. In order to establish whether more than one population of cholecystokinin-expressing interneurone exist in the hippocampus, we have performed whole-cell current clamp recordings from interneurones located in the stratum radiatum of the hippocampal CA1 region of developing rats. Recorded neurones were filled with biocytin to reveal their axonal targets, and were tested for the presence of pro-cholecystokinin immunoreactivity. The results show that two populations of cholecystokinin-immunoreactive interneurones exist in the CA1 area (n=15 positive cells). Cholecystokinin-positive basket cells (53%) preferentially innervate stratum pyramidale and adjacent strata oriens and radiatum. A second population of cholecystokinin-positive cells, previously described as Schaffer collateral-associated interneurones [Vida et al. (1998) J. Physiol. 506, 755-773], have axons that ramify almost exclusively in strata radiatum and oriens, overlapping with the Schaffer collateral/commissural pathway originating from CA3 pyramidal cells. Two of seven of the Schaffer collateral-associated cells were also immunopositive for calbindin. Soma position and orientation in stratum radiatum, the number and orientation of dendrites, and the passive and active membrane properties of the two cell populations are only slightly different. In addition, in stratum radiatum and its border with lacunosum of perfusion-fixed hippocampi, 31.6+/-3.8% (adult) or 26.8+/-2.9% (postnatal day 17-20) of cholecystokinin-positive cells were also immunoreactive for calbindin. Therefore, at least two populations of pro-cholecystokinin-immunopositive interneurones, basket and Schaffer collateral-associated cells, exist in the CA1 area of the hippocampus, and are probably homologous to cholecystokinin-immunopositive basket and double bouquet cells in the isocortex. It is not known if the GABAergic terminals of double bouquet cells are co-aligned with specific glutamatergic inputs. However, in the hippocampal CA1 area, it is clear that the terminals of Schaffer collateral-associated cells are co-stratified with the glutamatergic input from the CA3 area, with as yet unknown functional consequences. The division of the postsynaptic neuronal surface by two classes of GABAergic cell expressing cholecystokinin in both the hippocampus and isocortex provides further evidence for the uniform synaptic organisation of the cerebral cortex.

Cesium prevents maintenance of long-term depression in rat hippocampal CA1 neurons.

Long-term depression of field excitatory postsynaptic potentials (EPSP) in the CA1 region of hippocampal slices was evoked by delivering a 15 min train of pulses at 1 Hz to the Schaffer-commissural-CA1 pathway, and prevented by adding an N-methyl-D-aspartate (NMDA) receptor antagonist (AP-5, 50 microM) to the perfusing medium. Superfusion of the slices with Cs (2 mM) during the 1 Hz stimulation period could both inhibit the maintenance phase of the depression itself and elicit spontaneous rhythmic activity. Cs had no effect on the postsynaptic response to the GABA-B agonist, baclofen. As a major effect of Cs is a block of the hyperpolarization-activated current (Ih), these results suggest the possible involvement of Ih in the maintenance of long-term depression.